Extended system information distribution mechanisms

ABSTRACT

A disclosed method is implemented by a network node in a wireless communication network to transmitting system information to a plurality of wireless terminals. The network node transmits a first group of system information blocks (SIBs) via a first physical channel, and transmits a second group of additional SIBs via a different, second physical channel A corresponding network node operative to implement the method is also disclosed. Another disclosed method is implemented by a wireless terminal in a wireless communication network. The wireless terminal processes information received from a base station over a first physical channel to identify a first group of SIBs, and processes information received from the base station over a different, second physical channel to identify a second group of additional SIBs. A corresponding wireless terminal operative to implement the method is also disclosed.

PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 15/946,340 which is a continuation, under 35 U.S.C. § 120, ofU.S. patent application Ser. No. 14/768,250 filed on Aug. 17, 2015,which is a U.S. National Stage Filing under 35 U.S.C. § 371 ofInternational Patent Application Serial No. PCT/SE2014/050074 filed Jan.22, 2014, and entitled “Extended System Information DistributionMechanisms” which claims priority to U.S. Provisional Patent ApplicationNo. 61/769,073 filed Feb. 25, 2013, all of which are hereby incorporatedby reference in their entirety.

TECHNICAL FIELD

The subject matter described herein generally relates to wirelesscommunication networks. In particular, the subject matter relates tomethods, apparatuses, and/or systems for distribution of systeminformation. Terminologies from the Third Generation Partnership Project(3GPP) are used below only to facilitate explanation and exampleapplication. Wireless systems such as Worldwide Interoperability forMicrowave Access (WiMax), Ultra Mobile Broadband (UMB), Global Systemfor Mobile Communications (GSM), WiFi, and others may benefit from thetechnology described herein.

BACKGROUND

In a wireless network such as a 3GPP Wideband Code Division MultipleAccess (WCDMA) network, system information (SI) distribution providesthe ability to schedule and broadcast system information over thenetwork air interface. Typically, system information is generated in theRadio Network Controller (RNC) passed to the Radio Base Station (RBS)using the Node B Application Protocol (NBAP) procedure SystemInformation Update. RBS repeats the information periodically on theBroadcast Control Channel (BCCH) which is mapped to a Broadcast Channel(BCH) transport channel carried by the Primary Common Control PhysicalChannel (P-CCPCH) in the cell.

System information is grouped into different System Information Blocks(SIBs), where each SIB contains information elements of the same nature.Different system information blocks may have different characteristics,e.g., regarding their repetition rate and the requirements on UserEquipment (UEs) to re-read the information.

The Master Information Block (MIB), which is also broadcasted over theair interface, provides references and scheduling information to anumber of SIBs in the cell. The scheduling of the MIB is standardized by3GPP. The repetition period is 80 ms (every fourth 20 ms TransmissionTime Interval “TTI”) and the start position is System Frame Number(SFN)=0, i.e., the MIB is transmitted in every BCH TTI starting at SFNswhere (SFN mod 8)=0. SIB references can also be provided by separateScheduling Blocks (SBs). A scheduling block is always referenced fromthe MIB. FIG. 1 illustrates an example structure of SIBs.

The scheduling information in the MIB/SB provides a list of the SB/SIBstransmitted in the cell and their location on the broadcast channel. Thescheduling information also contains a value tag (or an expirationtimer) for each SIB that gives information to the UE about the versionand validity of the information currently sent on the broadcast channel.

Currently, to acquire the necessary SIBs transmitted on the broadcastchannel, the UE must first read the MIB to get references to the firstlevel of SIBs. After that the UE needs to read the Scheduling Block toget references to the remaining SIBs.

One RRC SI message is transmitted in each 20 ms TTI on the BCH using RLCtransparent mode. The SI message contains:

-   -   The system frame number (SFN) for the first radio frame in the        TTI;    -   a SIB segment and/or one or several complete SIBs (this        information is optional and only included if SIB data is        scheduled in the TTI).

If the SI message does not completely fill the transport block, paddingis added up to the transport block size of 246 bits.

Different update mechanisms apply for the SIBs depending on whether theycontain static or dynamic information. For SIBs containing staticinformation, a value tag is used to indicate when there is a need forthe UE to read new information on the broadcast channel. The SIB valuetag is sent together with the scheduling information in the MIB or inSB. Whenever the SIB content is modified, the corresponding SIB valuetag is updated by the network. Due to the layered structure, a change onthe lowest SIB level will propagate all the way up to the MIB, i.e.,both the SB- and the MIB value tags will be incremented as well. The newMIB value tag is signaled in message Paging Type 1 (on Paging Channel“PCH”) and System Information Change Indication (on the Forward AccessChannel “FACH” and High Speed Downlink Shared Channel “HS-DSCH”) tonotify the UEs about the updated system information. Once the UEreceives the notification, it will start from the top and compare thenew value tags signaled on the broadcast channel with the stored valuetags. If they differ, the UE needs to reacquire the SIB to get theupdated information.

For SIBs containing dynamic information, an expiration timer is used asan update mechanism. When the timer expires, the corresponding SIBinformation which the UE has stored is considered to be invalid and theUE must acquire the system information block again.

Note that a particular UE at a certain time may require validinformation only for a subset of all SIBs broadcasted in the cell. WhichSIBs the UE requires depends on the features supported by the UE and thecurrent RRC state (idle mode, PCH or FACH).

The existing system information distribution mechanism was introduced in3GPP Rel-99 and has not been changed since then. As a result of the HighSpeed Packet Access (HSPA) feature growth during the past RAN releases,the available BCH capacity of 12 kbps is almost filled up by existingMIB/SB/SIBs supporting features up to Rel-8.

In particular, the following problems related to the currentdistribution mechanism have been identified:

Fragmentation:

Although it is possible to concatenate the last segment (or firstsegment) of a SIB with one or several complete SIBs in the sametransport block, the BCH channel is getting more and more fragmented asthe number of SIBs and SIB segments increases. The main contributor isthe MIB that must be repeated on the broadcast channel every 4^(th) TTI,Even if the MIB itself does not occupy the full transport block, it isdifficult to use the remaining parts in an efficient way.

When more features are enabled in the network, the size of the existingSIBs (e.g., SIB3, SIB5 and SIB11) increases and there is a need toschedule more subsequent segments for each SIB. A subsequent segmentrequires a TTI of its own and cannot be concatenated with other completeSIBs or SIB segments, i.e., it cannot reuse unfilled parts of thetransport blocks. Mixing SIBs with different repetition periods alsogenerates “gaps” on the broadcast channel that can be hard to fillconsidering that the offset between two consecutive segments of the sameSIB is limited to 320 ms by the existing standard.

Scheduling Overhead:

The UE is informed about the exact position of each SIB segment as wellas the value tag (or expiration timer) and scope (“cell” or “PLMN”) ofthe SIB. When the number of SIB segments increases on the broadcastchannel, the scheduling overhead grow as well. The UE must first readthe scheduling information contained in the MIB and the SchedulingBlocks to find the positions of the SIBs to be acquired. Thus, it isimportant that the scheduling information be repeated frequently toensure that the overall time to read system information is acceptable.Today, the scheduling information occupies approximately 25% of thetotal BCH capacity.

Layered MIB/SB/SIB Structure:

The current SIB structure uses up to three layers which can delay thesystem information acquisition. When a SIB is modified, the UE mustfirst read the MIB, followed by the Scheduling Block, to find out whichSIB value tag has been changed. After that, the UE is able to read thenew SIB and update the corresponding information.

No DTX Support:

The current SIB structure does not support a DTX format to be used whenthere is no system information scheduled for the TTI (except the SFN).This costs unnecessary DL transmit power.

SUMMARY

According to one aspect of the present disclosure, a method isimplemented by a network node in a wireless communication network fortransmitting system information to a plurality of wireless terminals.According to the method, the network node transmits a first group ofSIBs via a first physical channel, and transmits a second group ofadditional SIBs via a different, second physical channel.

In one or more embodiments, the first physical channel is configured tobe read by a first group of wireless terminals and also by a different,second group of wireless terminals, and the second physical channel isconfigured to be read by only one of the first and second group ofwireless terminals. In one example, the first physical channel is theP-CCPCH, and the second physical channel is one of the S-CCPCH and theHS-PDSCH.

In one or more embodiments, the network node method also includes thenetwork node transmitting, via the first physical channel, schedulinginformation for reception of the additional SIBs on the second physicalchannel. The scheduling information may be included in a schedulingblock transmitted via the first physical channel.

In one or more embodiments, the network node method also includes thenetwork node transmitting, via the second physical channel, schedulinginformation for reception of the additional SIBs, and also transmitting,via the first physical channel, either additional scheduling informationfor reception of the additional SIBs or an indication that theadditional SIBs are going to be transmitted via the second physicalchannel.

In one or more of the embodiments discussed above, the transmitting ofthe second group of additional SIBs via the second physical channelincludes transmitting, via the second physical channel, one or morefirst SIBs that only include static system information, andtransmitting, via the second physical channel, one or more second SIBsthat only include dynamic system information.

A corresponding network node configured to implement the various networknode methods discussed above is also disclosed.

According to another aspect of the present disclosure, a method isimplemented by a wireless terminal in a wireless communication networkfor processing system information. The wireless terminal processesinformation received from a base station over a first physical channelto identify a first group of SIBs, and also processes informationreceived from the base station over a different, second physical channelto identify a second group of additional SIBs.

In one or more embodiments, the first physical channel is configured tobe read by a first group of wireless terminals and also by a different,second group of wireless terminals, and the second physical channel isconfigured to be read by only the second group of wireless terminals. Insuch embodiments, the wireless terminal is part of the second group ofwireless terminals. In one example, the first physical channel is theP-CCPCH, and the second physical channel is one of the S-CCPCH and theHS-PDSCH.

In one or more embodiments, the wireless terminal identifies the secondgroup of additional SIBs based on processing information received fromthe base station over the first physical channel to identify schedulinginformation for reception of the additional SIBs on the second physicalchannel.

In one or more embodiments, the wireless terminal method also includesthe wireless terminal processing information received from the basestation over the second physical channel to identify schedulinginformation for reception of the additional SIBs. In these embodiments,the wireless terminal method also includes processing informationreceived from the base station over the first physical channel toidentify either additional scheduling information for reception of theadditional SIBs or an indication that the additional SIBs are going tobe transmitted via the second physical channel.

In one or more embodiments, the processing of information received fromthe base station over the second physical channel to identify the secondgroup of additional SIBs includes identifying, from the informationreceived over the second physical channel, one or more first SIBs thatonly include static system information, and identifying, from theinformation received over the second physical channel, one or moresecond SIBs that only include dynamic system information.

A corresponding wireless terminal configured to implement the variouswireless terminal methods discussed above is also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example SIB structure.

FIG. 2a illustrates an example SIB structure according to a firstembodiment.

FIG. 2b illustrates an example network node method for the SIB structureof FIG. 2 a.

FIG. 2c illustrates an example UE method for the SIB structure of FIG. 2a.

FIG. 3a illustrates a SIB structure according to a second embodiment.

FIG. 3b illustrates an example network node method for the SIB structureof FIG. 3 a.

FIG. 3c illustrates an example UE method for the SIB structure of FIG. 3a.

FIG. 4a illustrates an example SIB structure according to a thirdembodiment.

FIG. 4b illustrates an example network node method for the SIB structureof FIG. 4 a.

FIG. 4c illustrates an example UE method for the SIB structure of FIG. 4a.

FIG. 5a illustrates an example SIB structure according to a fourthembodiment.

FIG. 5b illustrates an example network node method for the SIB structureof FIG. 5 a.

FIG. 5c illustrates an example UE method for the SIB structure of FIG. 5a.

FIG. 6 illustrates an example mapping of SIB segments to SI messages.

FIG. 7 illustrates an example MAC PDU for transmission on a RACH.

FIG. 8 illustrates an example coding for a TCTF field of the MAC PDU ofFIG. 7.

FIG. 9 illustrates an example MAC-i PDU.

FIG. 10 illustrates an example header for the MAC-i PDU of FIG. 9.

FIG. 11 illustrates an example LCH-ID field coding for the MAC-I headerof FIG. 10.

FIG. 12 illustrates an example on-demand distribution of systeminformation.

FIG. 13 illustrates an example PICH channel structure.

FIG. 14 illustrates an example AICH channel structure.

FIG. 15 illustrates an example P-CCPCH frame structure.

FIG. 16 illustrates an example method implemented by a network node fortransmitting system information to a plurality of wireless terminals.

FIG. 17 illustrates an example method implemented by a wireless terminalfor processing system information received over different physicalchannels.

FIG. 18a illustrates the main functional elements of an example networknode capable of distributing system information using one or more of thetechniques described above.

FIG. 18b illustrates an example hardware configuration for the networknode of FIG. 16 a.

FIG. 19a illustrates the main function elements of an example wirelessterminal capable of processing system information using one or more ofthe techniques described above.

FIG. 19b illustrates an example hardware configuration for the wirelessterminal of FIG. 17 a.

DETAILED DESCRIPTION

To accommodate new system information on the broadcast channel, theexisting system information may be transmitted less often.Unfortunately, this will result in longer time for the UE to acquire thenecessary SIBs, i.e., increase latency. This could, for example,increase the call setup- and up-switch times from URA/FACH as well asthe outage times at IRAT and Inter-frequency cell reselection.Considering that UEs will spend more time in URA/PCH and CELL_FACHstates in the future, it is extremely important to minimize performancedegradation performance of these states.

The format of the existing broadcast channel may be modified toaccommodate the new system information. But note that the broadcastchannel is read and needs to be understood by all UEs currently deployedin the networks. All SIBs needed for these legacy UEs need to betransmitted using the existing Rel-99 framework for system informationdistribution. This implies that there is very limited flexibility tochange the format of the existing broadcast channel.

In order to secure the growth for coming releases (e.g., upcoming HSPAreleases), there is a need to extend the system information capacity,while maintaining backwards compatibility for the existing UEs.

As indicated above, it is desired to extend the system informationdistribution mechanism to accomplish the following goals (among others):

-   -   Accommodate distribution of new system information;    -   Maintain compatibility with legacy UEs;    -   Minimize latencies.

In one or more aspects, a network may utilize a plurality of (i.e., twoor more) system information distribution channels to distribute thesystem information to the wireless terminals (e.g., UEs). For example,first, second, third . . . etc. distribution channels may be used. Atleast one distribution channel, e.g., the first distribution channel,may be used maintain backwards compatibility with the currently existingSI distribution mechanism. The first distribution channel may also bereferred to as a legacy distribution channel. At least one otherdistribution channel, e.g., the second distribution channel, may be usedto extend the SI distribution mechanism for those UEs that capable ofunderstanding the extended mechanism. The second distribution channelmay also be referred to as an extended distribution channel.

In the following, SI distribution using first (legacy) and second(extended) SI distribution channels will be described. However, thescope of description can be extended to cover more than two distributionchannels.

For ease of reference, the existing SI distribution mechanism for SIbroadcast may be referred to as “Broadcast 1” or “BC1.” As anillustration, the SI broadcast as specified by 3GPP Rel-99 framework maybe considered to be an example of the BC1 mechanism. The scope of theBC1 mechanism may cover all protocols (e.g., NBAP, RRC, L1) and channels(logical channel: BCCH, transport channel: BCH, physical channel:P-CCPCH) used for existing system information distribution.

The SI broadcast for the extended distribution may be referred to as“Broadcast 2” or “BC2.” It is intended that the scope of the BC2mechanism covers protocols and channels (logical channels/transportchannels/physical channels) to be used for the new system informationdistribution mechanism.

Embodiments of SIB Structures for Extended SI Distribution

Examples of multiple mechanisms to extend the SI distribution arepresented below. In a first embodiment, the existing BC1 mechanisms arereused as much as possible. An example SIB structure is illustrated inFIG. 2a . The scheduling information in the SB-BC1 in the firstdistribution channel may be extended to enable references to the newSIBs transmitted on the second distribution channel. The informationincluded in the SB-BC1 may include any one or more of:

-   -   a SIB type which identifies the SIBs (e.g., SIB m+1 . . . SIB        x). The SIB type may implicitly indicate that the SIB is        transmitted on the second distribution channel utilizing the BC2        mechanism;    -   an explicit indication that the SIB is transmitted on the second        distribution channel utilizing the BC2 mechanism;    -   an indication whether the area scope of the SIB is “cell” or        “PLMN”;    -   a value tag if the SIB includes static information;    -   an expiration timer if the SIB includes dynamic information;    -   a start position (e.g., SFN) on the second distribution channel        where the first SIB segment (e.g., SIB m+1) is scheduled and        optionally one or several offset parameters if the subsequent        SIB segments are not sent in consecutive TTIs;    -   a repetition period indicating how often the SIB is repeated on        the broadcast channel.

While not illustrated in FIG. 2a , the scheduling block in the MIB inthe first distribution channel may be extended to refer to the SIBstransmitted on the second distribution. Also, both the MIB and the SBmay be extended.

FIG. 2b illustrates an example of a method performed by a network node(e.g., RNC, RBS) to distribute system information using the SIBstructure of FIG. 2a . It should be noted that the order of transmittingMIB/SB-BC1 on the first channel and the new SIB on the second channel isnot particularly significant. They may be transmitted sequentially oneafter the other or in parallel. They may even partially or totallyoverlap. In this and in other embodiments described below, the sameconcept may apply. That is, unless otherwise explicitly indicated, theorder of the SIB related information transmitted from the network nodeis not particularly significant.

The UE may use the legacy BC1 acquisition mechanisms to find thereferences to the new SIBs on BC2. For example, based on the SIB type(or the new BC1/BC2 indicator), the UE may read the SIB on either BC1 orBC2. Above, it is indicated that the SIB type may implicitly indicatethat the SIB is transmitted on the second distribution channel. But alsoas indicated, this information may be explicitly indicated. This can beuseful in circumstances where the SIB type by itself is insufficient toconclude that the SIB is transmitted on the second distribution channel.

FIG. 2c illustrates an example method performed by a UE to access thenew SIB of FIG. 2a on a second distributions channel. Just as theMIB/SB-BC1 and the new SIBs may be transmitted by the network in anyorder, the UE may also receive the same in any order. The UE may receiveand store the received information in any order. However, the receivedinformation may be decoded in the order illustrated in FIG. 2c . In thisand other embodiments described below, the UE may receive the SIBrelated information transmissions (and store them) in a random orderunless specifically stated otherwise.

Before proceeding further, the following should be noted. The newSIBs—those that are not understood by the legacy UEs—may be transmittedutilizing the extended mechanism BC2. However, this does not necessarilypreclude using the second distribution channel to transmit existing SIBsthat are understood by the legacy UEs. For example, SIB m+1 may be anexample of a new SIB (not understood by legacy UEs) and SIB x may be anexample of a legacy SIB. One (of which there can be several) reason forutilizing the BC2 mechanism to transmit legacy SIBs may to balance theload of distributing the SIBs. This concept of possibly utilizing theBC2 mechanism to distribute legacy SIBs may apply to the firstembodiment, and to some or all of the other embodiments described below.

In this embodiment, legacy update mechanisms may be reused. When thenetwork (e.g., the RNC, RBS) modifies the content of a SIB transmittedon the second distribution channel, the network may also increment theSIB value tag contained in SB-BC1. The change may propagate up to theMID on BC1, and the new MIB value tag may be signaled to the UE, e.g.,on the PCH and FACH/HS-DSCH transport channels, using the legacynotification messages. For dynamic SIBs, expiration timers may be used.

FIG. 3a illustrates an example of a second embodiment of the SIBstructure. In this embodiment, the scheduling block (SB-BC1) or the MIBin the first distribution channel may point to a new extended schedulingblock (SB-BC2) on the second distribution channel. SB-BC2 in turn maylist and provide scheduling information for the SIBs transmitted on thesecond distribution channel.

FIG. 3b illustrates an example of a method performed by a network node(e.g., RNC, RBS) to distribute system information for the SIB structureof FIG. 3a . The scheduling information for SB-BC2 provided in SB-BC1,or in the MIB, may include some or all of the information elementslisted for the first embodiment describe above (e.g., area scope, valuetag/expiration timer, start position, offset and repetition period).Similarly, the SB-BC2 can include some or all of the schedulinginformation elements per referenced SIB, or a subset of the information.The SIBs on BC2 can also be referenced using a new set of schedulinginformation elements included in SB-BC2. Again, the order is notparticularly significant.

In this second embodiment, the UE may first use the legacy BCacquisition mechanisms to find a reference to the new Scheduling Blockon BC2. Once the SB-BC2 has been acquired, the UE can then find theremaining SIBs on second distribution channel.

FIG. 3c illustrates an example method performed by the UE to access theSIB of FIG. 3a on a second distributions channel. Again, the order ofoperations in FIG. 3c may indicate the order of decoding the receivedinformation—it does not necessarily indicate the order of informationreception.

Similar to the first embodiment, legacy update mechanisms may be reusedfor the second embodiment. When the network modifies the content of aSIB transmitted on the second distribution channel, the network may alsoincrement the SIB value tag contained in SB-BC2. The change maypropagate up to the MIB on BC1 via the SB-BC1, and the new MIB value tagmay be signaled to the UE, e.g., on the PCH and FACH/HS-DSCH transportchannels, using the legacy notification messages.

FIG. 4a illustrates an example of a third embodiment of the SIBstructure. In this embodiment, the presence of BC2 may be indicated inthe MIB or in SB-BC1 on the first distribution channel using a new “BC2indicator” (second distribution channel indicator). The MIB and/orSB-BC1 may include the BC2 indicator information element.

When BC2 is enabled and the “BC2 indicator” is set, the network node mayrepeat the scheduling block on BC2 using a start position and repetitionperiod. One or both of the start position and the repetition period maydefault to predetermined values. For example, they may be defined by astandard (e.g., 3GPP). In an alternative, the start position and/or therepetition period may be provided in the MIB and/or the SB-BC1. As yetanother alternative, there may be default start position and/orrepetition period that can be superseded by the values provided in theMIB and/or the SB-BC1. Compared to the first and second embodimentsdescribed above, the third embodiment may minimize the additionalscheduling overhead that needs to be included on BC in order to supportBC2.

SB-BC2 may include a value tag to indicate the version of the containedinformation as well as a list of the SIBs transmitted on BC2 plusrelevant scheduling information. The scheduling information may includesome or all scheduling information elements listed for the first and/orsecond embodiments. Also, new set of information elements may beincluded.

FIG. 4b illustrates an example of a method performed by a network node(e.g., RNC, RBS) to distribute system information using the SIBstructure of FIG. 4a . In this third embodiment, the UE will understandwhether or not BC2 is supported in the cell based on informationtransmitted on BC1 (e.g., the “BC2 indicator”). If this indicator isset, the UE may read the new scheduling block SB-BC2 on the seconddistribution channel. The SB-BC2 may be located on a predeterminedposition on the BC2. Once the SB-BC2 is acquired, the UE then can findthe remaining SIBs on second distribution channel.

FIG. 4c illustrates an example method performed by the UE to access theSIB of FIG. 4a on a second distributions channel. In this thirdembodiment, the legacy update mechanisms can be reused to some extent.However, a new SB-BC2 value tag may be included in the Paging Type 1 andSystem Information Change Indication messages. This value tag may besent to the UE whenever the content of a BC2 SIB is modified. Atreception of the notification (e.g., on PCH, or FACH/HS-DSCH), the UEmay check the SB-BC2 and compare the new value tags for the BC2 SIBswith the stored ones. If they differ the UE may reacquire the modifiedSIB.

FIG. 5a illustrates an example of a fourth embodiment of the SIBstructure. Unlike the first three embodiments, the new systeminformation to be transmitted on BC2 may be grouped into two separateSIBs depending on how frequent the information is changed by thenetwork. As seen, all static information may be provided in one SIB(denoted SIB-S in FIG. 5a ) and all dynamic information may be providedin one SIB (denoted SIB-D in FIG. 5a ).

The presence of BC2 in the fourth embodiment may be indicated in the MIBor in SB-BC1 on the first distribution channel using the new “BC2indicator”, which is similar to the third embodiment. When BC2 isenabled and the “BC2 indicator” is set, the network node may repeat thestatic SIB-S on the second distribution channel using a start positionand repetition period. One or both of the start position and therepetition period may default to predetermined values. For example, theymay be defined by a standard (e.g., 3GPP). In an alternative, the startposition and/or the repetition period may be provided in the MIB and/orthe SB-BC1. As yet another alternative, there may be default startposition and/or repetition period that can be superseded by the valuesprovided in the MIB and/or the SB-BC1.

In addition to the static information, the SIB-S may also include one orboth of the following:

-   -   A value tag to indicate the version of the contained information        in SIB-S;    -   Information about the dynamic SIB-D. For example, the presence        and position of SIB-D on the second distribution channel (this        is considered to be static information).

FIG. 5b illustrates an example of a method performed by a network node(e.g., RNC, RBS) to distribute system information using the SIB of FIG.5a . Grouping all static data in the same SIB implies that theinformation is transmitted on the broadcast channel using the samerepetition period. This can be acceptable since in most cases, there maybe little to no benefit in getting a subset of the static BC2information before the UE has been able to read all legacy informationon BC1. Thus, the SIB-S acquisition is not time critical and therepetition period can be set to the largest possible value that matchesthe time it takes for the UE to read the legacy SIBs on BC1.

Furthermore, when the static information is grouped in the same SIB, theUE reads all SIB segments in order to decode the information, includinginformation related to non-supported features, or other RRC states.However, the SIB-S data is only acquired by the UE when a new cell isentered (and no stored information with matching value tag exists), orwhen the SIB-S content is changed. Thus, the additional cost to readmore information than needed can be neglected.

SIB-D may include all dynamic system information and may be repeated onthe second distribution channel with a start position and repetitionperiod. For example, they may be defined by a standard (e.g., 3GPP). Inan alternative, the start position and/or the repetition period may beprovided in the SIB-S, MIB and/or the SB-BC2. As yet anotheralternative, there may be default start position and/or repetitionperiod that can be superseded by the values provided in the SIB-S, MIBand/or the SB-BC2.

The content of SIB-D can be associated with one or several expirationtimers controlling how often the UE must re-read the information. Forexample, one subset of the information elements listed in SIB-D can beassociated with Expiration timer 1, and another subset of theinformation elements can be associated with Expiration timer 2. TheExpiration timers can be set to different values depending on howfrequently the information is changed by the network. Typically theExpiration timer is equal to or longer than the SIB-D repetition period.

The Expiration timers controlling how often the UE must acquire SIB-Dinformation can, for example, be included in either SIB-S (as it can beconsidered to be static information) or in SIB-D (as the timers must bereferenced in SIB-D anyway).

In this third embodiment, the UE will understand whether or not BC2 issupported in the cell based on information transmitted on BC1 (e.g., the“BC2 indicator”). If this indicator is set, the UE may find the staticinformation in SIB-S on a predetermined position on BC2 (standardized orprovided in the MIB or SB on BC1). Once the SIB-S is acquired, the UEthen can find out whether any dynamic data is broadcasted in the cell,and where this information is scheduled on BC2.

FIG. 5c illustrates an example method performed by the UE to access theSIB-S and SIB-D of FIG. 5a on the second distributions channel. In thisfourth embodiment, the legacy update mechanisms can be reused to someextent. However, a new SIB-S value tag may be included in the PagingType 1 and System Information Change Indication messages. This value tagmay be sent to the UE whenever the content of a SIB-S is modified. Atreception of the notification (e.g., on PCH, or FACH/HS-DSCH), the UEmay read and store a new version of the SIB-S.

Mapping of SIBs to SI Messages

The new SB/SIBs to be transmitted on second distribution channel may beencoded and segmented in the RNC. The RNC may then pass the encodedSB/SIB segments and relevant scheduling information to the RBS, e.g., byusing the NBAP procedure System Information Update. RBS may then map theSIB segments to System Information (SI) messages and repeat theinformation on the channel according to the scheduling informationprovided by RNC.

New system information may be sent to the RBS only when the SIB isgenerated the first time (typically when the cell is activated or when aspecific SB/SIB is enabled), or when the SB/SIB content is modified.

In one embodiment, the new SIB types on the second channel may besegmented and re-assembled using the existing SIB segmentation protocol,e.g., as specified in [1] where it is possible to concatenate SIBsegments and/or complete SIBs from several SIB types in the same SImessage. The existing NBAP procedure, e.g., as specified in [2], may beextended with new information to support the transfer of the new BC2SB/SIB types. In the RBS, the new SB/SIB segments may be mapped to SImessages that are transmitted over the Uu interface, e.g., using the RLCtransparent mode. The existing SI message, e.g., as specified in [1],may be reused except for the information element (IE) “SFNprime” (11bits) that may be omitted when the SI message is sent on the secondchannel.

In an embodiment, the new SIB types on BC2 may be segmented using a newsimplified segmentation protocol as outlined in FIG. 6. This protocolcan be optimized for a configuration where no concatenation is allowedand each SI message only contains one SIB Type. It can for example beapplied for the fourth embodiment described above where BC2 onlycontains two SIB types (SIB-S and SIB-D).

After RRC ASN.1 encoding, the SIB may be segmented into equally largesegments. For the last segment padding may be added to fill up thetransport block size. The RNC may transfer segments and relevantscheduling information to the RBS, e.g., using the existing NBAPprocedure System Information Update. RBS may map each segment to oneSystem Information (SI) message that is sent over the Uu interface,e.g., using RLC transparent mode.

The SI Message may include a SI header and a payload containing only oneSIB segment (first, subsequent or last segment). The SI header mayinclude a fixed length and could contain, but is not limited to, thefollowing information:

-   -   SIB ID—identifies the SIB type contained in the SI message. For        the fourth SIB structure embodiment, this field may indicate if        the SI message includes a SIB-S or a SIB-D segment;    -   SN—Sequence number for the SIB segment. For example, the first        segment of a SIB may have SN=0, the subsequent segment has SN=1,        etc. (the starting value of SN may be any number);    -   L—Indicates if this is the last segment of the SIB (TRUE/FALSE).

Preferably, the size of the payload will match the size of the transportblock used to carry the information on the physical layer.

In another embodiment, no segmentation is performed and one complete SIBmay be mapped to one SI message. In this instance, the SI message mayinclude a very simple SI header (to inform the UE about the SIB type)and payload.

For all alternatives described above, the UE should be able to storesuccessfully received SI messages even if they are received out ofsequence order. When all segments belonging to the same SIB ID have beenacquired, i.e., all segments from SN=0 until the last segment indicatedby L=TRUE, the UE may assemble the segments in sequential order anddecode the complete SIB.

SI Scheduling Alternatives

Predetermined Scheduling:

The above described embodiments, predetermined scheduling of SI messagesmay be implement in which the exact position is known from thescheduling information (or standardized, e.g., by 3GPP). Inpredetermined scheduling, a frame structure or a numbering oftransmission instants such as SFN or sub frame number may be necessary.If the start position and repetition period is known, the location ofthe SI message may be given by the formula below:(transmission_instant mod repetition_period)=start_positionIn addition to the predetermined scheduling, the following alternativescheduling options may be considered as well.

Flexible Scheduling:

If the UE must monitor the second distribution until all required systeminformation is received, this could result in unnecessary reading totake place. For information that is not read very often (e.g., staticinformation), this may be acceptable. But this may not be optimal if UEsneed to acquire dynamic information more frequently (e.g., dynamicinformation). In these instances, the network may ensure that all systeminformation is transmitted often enough, i.e., with a predeterminedfrequency, but apart from that, the network may have full flexibilitywhen this information is transmitted.

Semi-Flexible Scheduling:

In this alternative, the UE is aware of the scheduling window for the SIMessage, within which the UE must monitor all potential transmissioninstants. The network in this case may ensure that the SI messages aretransmitted within their respective scheduling windows.

Note that when the scheduling window in the semi-flexible schedulingcoincides with the full repetition period of the second distributionchannel system information, this is the same as flexible scheduling. Inthe following semi-flexible scheduling will be referred when going intodetails, but it should be understood that the same principles couldapply even for flexible scheduling.

On-Demand Scheduling:

In this alternative, the system information is not sent periodically onthe broadcast channel. Rather, UE may request the information, e.g.,when entering a new cell for which the UE has no stored information.This scheduling option makes it possible to use a more aggressive DTXscheme as the information may be sent only when a UE needs it. The UEmay request the system information using different means. Examples ofsuch means are described below.

Mapping of SI Messages to Physical Layer

As described above, the higher layers (e.g., Medium Access Control“MAC”, Radio Link Control “RLC”, and Radio Resource Control “RRC”) maysegment the system information into a number of SI messages that are tobe transmitted at given times or within given time intervals. These SImessages will then have to be mapped to the physical layer andtransferred over the Uu interface to the UE. This section outlinesalternatives for how this mapping can be done.

Mapping to Common Control Channel:

The Secondary Common Control Physical Channel (S-CCPCH) is a physicalchannel that in existing standard is used to transfer the FACH and PCHtransport channels. One alternative is to use this already specifiedchannel also for SI message distribution. The SI messages would then bemapped to an already existing transport channel such as FACH, PCH orBCH, or to a new defined transport channel. For simplicity, let BC2TrCHdenote the transport channel used for this purpose. The BC2TrCH wouldthen be mapped onto the S-CCPCH physical channel.

In a preferred embodiment, an additional S-CCPCH may be allocated tocarry the BC2TrCH and no other multiplexed transport channel. However,in other embodiments, it is also possible to multiplex the BC2TrCH withFACH and/or PCH onto an existing S-CCPCH, thereby avoiding the need tosetup an additional S-CCPCH just for the purpose of BC2TrCHtransmission.

Also in a preferred embodiment, each SI message corresponds to onetransport block on the BC2TrCH. In other exemplary embodiments, multipleSI messages may be mapped to one transport block, or one SI messagecould be mapped to multiple transport blocks.

On the current BCH/P-CCPCH, one transport block of size 246 bits istransmitted every 20 ms TI. The SI message mapped to the transport blockincludes an 11 bit long SFN. Since there is no need to transfer the SFNalso on the second distribution channel, one embodiment would be toreduce the total SI message size with 11 bits by excluding the SFN bits,and map this to a 246−11=235 bit transport block. This is advantageousin that the available payload in the SI message for SIB data would beunchanged, and hence existing segmentation mechanisms could be employed.Further, the existing one-to-one mapping between a SI message and atransport block may be retained.

Other alternatives would be to actually include the SFN or insertpadding in those bits also on second distribution channel, and maintainthe entire structure based on the existing 246 bit transport blocks andSI messages.

A restriction on the current BCH/P-CCPCH is that one transport block istransmitted in each TTI. When mapping SI messages onto the S-CCPCH, itis possible to let the BC2TrCH carry more than one transport block perTTI. Assuming a one-to-one mapping between SI messages and transportblocks, this implies transmission on multiple SI messages in one TTI.One benefit with allowing multiple transport blocks per TTI is that thetransport block size, and hence SI message size, can be kept small, Withsmaller SI messages, the need for padding in the higher layersegmentation is reduced.

Further, a longer TTI provides more interleaving benefit on fadingchannels, and can lead to lower required transmit power to achieve acertain block error rate in the UE's detection of the BC2TrCH. However,with longer TTIs, the number of bits contained in the TTI may increase.By splitting these bits over multiple transport blocks, the benefitswith long TTI can be obtained without the drawback of longer transportblocks and more padding. By allowing only a subset of the transportblocks in the TTI to be transmitted, the power used during the TTI willbe lower than if all transport blocks were transmitted.

When receiving a BC2TrCH with more than one possible transport block perTTI, the UE can then apply blind transport format detection and attemptto decode the maximum number of transport blocks in one TTI. If only asubset of the possible transport blocks is transmitted, the UE wouldthen detect a CRC error when trying to detect a non-existent transportblock. For some segmentation solutions, the UE may be aware of thedetails of the higher layer segmentation of system information into SImessages (in particular how many SI messages it is expected to receiveand sequence numbering of these SI messages or the data containedtherein). In these cases, the UE can deduce if the CRC error correspondsto a transmitted (expected) but faulty received transport block, or to anon-transmitted (non-expected) transport block. The UE can also limitits detection attempts to only the expected transport blocks, byemploying the knowledge of higher layer segmentation.

In the above paragraph it is assumed that no Transport FormatCombination indicator (TFCI) is transmitted for the BC2TrCH TTIs, andthat the UE performs blind detection. However, in an embodiment, it isalso possible to include a TFCI and let the UE decode this TFCI and thendecode the signaled/detected transport format. However, a drawback withthis solution is the additional overhead from the TFCI bits.

A further restriction on the current BCH/P-CCPCH is that one transportblock must be transmitted each TTI. This is because the SFN needs to betransmitted every IT, even if there is no other SI data to be sent. Inthese cases almost all bits in the 246 bit transport block will bepadding bits, which just consume downlink power without conveyingadditional information to the UE.

But in an embodiment, since the SFN is available to the UE on the legacychannels, there is no need to send the SFN on the second distributionchannel. Hence, during time instants (TTIs) where there is no SIinformation or SFN information, the SI messages need not be transmitted.It would then be beneficial to allow these TTIs to go empty, i.e., theS-CCPCH carrying the BC2TrCH will not transmit any bits/power duringthese TTIs. To allow this, the BC2TrCH may include a transport formatcorresponding to no transmitted bits (zero rate), e.g., a transportformat with zero transport blocks.

Hence, in its most general form, the BC2TrCH would be defined to have anumber of transport formats, including a zero rate transport format. Ina preferred embodiment the transport format set would include thefollowing transport formats:

-   -   TF_N: N transport blocks, each of size TB_size,        where TF_N is the Nth transport format, N=0, 1, . . .        max_number_of_transport_blocks_in_TTI. It is expected that the        transport block size TB_size would be in the range 100-250 bits,        but other values are also possible.

It may be necessary for the UE to be aware of the spreading factor andslot format of the channelization code used for S-CCPCH and thechannelization code used for S-CCPCH. Either of these may bestandardized (e.g., predetermined in the 3GPP specifications) orprovided via higher layer signaling on the first distribution channel.

In one preferred embodiment, the BC2TrCH may be mapped to an S-CCPCHusing slot format #0. This is a slot format with a predeterminedspreading factor (e.g., 256, which provides sufficient bit rate for thesecond distribution channel while at the same time consuming as littledownlink code resources as possible), no pilot bits (P-CCPCH may be usedas phase reference as for the existing P-CCPCH) and no TFCI bits (blindtransport format detection may be performed by the UE). If a TFCI needsto be supported as well, then a slot format with TFCI bits should beused, such as slot format #2. Yet another solution would be to define anew slot format on S-CCPCH tailor made for the application of carryingthe BC2TrCH.

The TTIs on the BC2TrCH/S-CCPCH can be numbered (e.g., using the SFN orCFN), and hence it is possible for higher layers to indicate when intime different SI messages shall be transmitted over the Uu interface.

An S-CCPCH has an offset from the P-CCPCH frame timing, so that arelation between SFN and CFN timing is defined. In a preferredembodiment, this time offset may be set to zero so that the S-CCPCH usedfor second distribution channel has identical frame timing as P-CCPCH,and CFN and SFN terms denote the same thing. Higher layers may thenindicate in which SFNs the SI messages should be transmitted on the Uuinterface. For example, if a SI message is to be scheduled at SFN=42,then the corresponding BC2TrCH TTI would be mapped to a number ofS-CCPCH radio frames, where the first S-CCPCH radio frame starts duringthe P-CCPCH radio frame corresponding to SFN=42.

For the common control physical channel (e.g., S-CCPCH) alternative, itmay make most sense to let higher layers point out exactly in which TTIthe different SI messages are to be transmitted (predeterminedscheduling). This is because the BC2TrCH in the preferred embodiment maybe mapped to its own radio resources (channelization code), and hencethere would be less need to synchronize the activity on this channelwith other downlink channels. It is however possible to envision schemeswhere higher layers provide larger flexibility and the mapping of SImessages to SFNs is more flexible (flexible or semi-flexiblescheduling).

Mapping to new Physical Channel Type:

In the previous section S-CCPCH was considered as the physical channelcarrying BC2TrCH. It should be understood that a new physical channelwith similar characteristics as the S-CCPCH may be used instead. If sucha channel is defined, it could have slot formats tailor made for theapplication of carrying BC2TrCH. In its basic form, the slot format mayinclude only data bits (similar to slot format #0 on S-CCPCH). Onepossible extension would be to let the new physical channel also includebits in the slot format to be used as an indicator of the presence ofthe second distribution channel. Another possible extension would be toinclude bits in the slot format to carry the SI distribution in progressflag described below.

Mapping to Shared Channel:

The High Speed Physical Downlink Shared Channel (HS-PDSCH) is a physicalchannel that in existing standard is used to transfer the HS-DSCHtransport channel. One alternative is to use this already specifiedchannel also for SI message distribution. The SI messages would then bemapped to the blocks of the transport channel (e.g., HS-DSCH), and thesetransport blocks would then be mapped onto the physical channel(s)(e.g., HS-PDSCH).

For the already standardized functionality “IS in CELL_FACH”,BCCH/CCCH/DCCH logical channels are mapped to MAC-c Protocol Data Units(PDUs) for transmission on the HS-DSCH. In an embodiment, the MAC-ehsprotocol may be used which enables the possibility to send one orseveral MAC-c PDUs in one transport block, and even to segment one MAC-cPDU into several parts and transmit these parts in different transportblocks (potentially together with other MAC-c PDU segments).

The above HS in CELL_FACH functionality can be reused also for seconddistribution channel. In a preferred embodiment, each SI message wouldbe mapped to a MAC-c PDU, and these MAC-c PDUs would be forwardedthrough the MAC-ehs protocol layer to be mapped to transport blocks onthe HS-DSCH. In the following, such MAC-c PDUs carrying SI messages arereferred to as “SI MAC-c PDUs”.

Note that for BC2, there may be no corresponding uplink. Thus, nofeedback of ACK/NACK information to HS-DSCH transmissions may bepossible. Taking into account that there may be no ACK/NACK feedback, itis possible to have continuous transmission in consecutive TTIs even byusing only one Hybrid Automatic Repeat Request (HARQ) process (no needto wait for HARQ ACK/NACK). However, it is also possible to use theconcept of multiple HARQ processes (typically 6), in which MAC-ehs PDUsare put for transmission in a specific TTI.

To aid detection of the HS-DSCH/HS-PDSCH, the High Speed Shared ControlChannel (HS-SCCH) control channel, which is an example of a sharedcontrol channel, has been standardized. By employing the shared controlchannel, the UE may be made aware of exactly what Transport Format andResource Combination (TFRC) that is used on the data channel(s) (e.g.,HS-PDSCH(s)). These include, among others, the channelization codesused, modulation (e.g., Quadrature Phase Shift Keying “QPSK”/16Quadrature Amplitude Modulation “16QAM”/64QAM) and transport block size.When a HS-SCCH is used, a masking (scrambling) based on the HS-DSCHRadio Network Temporary Identifier (H-RNTI) is applied to the HS-SCCH,so that only UEs using this specific H-RNTI in its HS-SCCH detectionwill be able to decode the HS-SCCH. There is also some possibility torun without HS-SCCH, so called HS-SCCH-less operation, in which the UEtries to detect the HS-PDSCH directly (blindly, without detailedinformation about the used TFRC). To enable this, the UE may be informedin advance of a limited subset of used TFRCs, which the UE then can tryto detect blindly.

In one embodiment, the SI MAC-c PDUs may be transmitted on the datachannel (e.g., HS-DSCH) with an accompanying HS-SCCH. In this case, itmay be necessary for the UEs listening for BC2 to know which HS-SCCHmessages are associated with BC2. In one preferred embodiment, this canbe achieved by allocating a separate H-RNTI for the BC2 information.This H-RNTI can be defined already in the specifications (hard-coded) orsignaled to the UE on the BC1. This H-RNTI could be common for all (or agroup of) UEs or be UE specific. UEs in the process of receiving SI onBC2 would then listen for the shared control channel (e.g., HS-SCCH)messages addressed to this specific H-RNTI. When the shared controlchannel message is detected, the UE then may proceed to detect theHS-DSCH carrying the SI MAC-c PDUs.

A drawback with using an HS-SCCH associated with BC2 is that the powerrequired for the HS-SCCH to cover the entire cell can be rather high.Hence, in another embodiment, the SI MAC-c PDUs may be transmitted onHS-DSCH without any accompanying HS-SCCH. In this case, only a smallsubset (a predetermined number) of allowed TFRCs may be used fortransmission. This subset can be defined already in the specifications(hard-coded), or signaled to the UE on the BC1.

In yet another embodiment, a new control channel (e.g., new HS-SCCHtype) may be introduced for conveying BC2 information. This new controlchannel type (which may be a shared type) may be tailored for SI MAC-cPDUs and designed to consume as little power as possible. For example,only a few (predetermined number of) TFRCs may be supported, a fixedmodulation and a fixed number of codes. Also, various coverageenhancement features, such as repetition could be employed.

A benefit with mapping SI messages to a data channel (e.g., HS-PDSCH) isthat different transport formats can be used depending on availableresources (power, HS-PDSCH codes) and amount of system information tobroadcast. This is especially true for the case of flexible orsemi-flexible scheduling, where the distribution of SI messages can besteered towards TTIs where there are more available resources (e.g., noother data to be transmitted to any UE in these TTIs).

For the case of predetermined scheduling, each ST MAC-c PDU may beassociated with a specific transmission time when the PDU shall betransmitted over the Uu interface. This transmission time may be relatedto the SFN and subframe number of the HS-PDSCH. Hence, within thepriority queue (PQ) associated with these PDUs, the MAC-c PDUs will havean associated transmission time when PDUs need to be transmitted. Thescheduler may then need to ensure that priority is given to the PQ withSI MAC-c PDU with a transmission time that corresponds to the TTI to bescheduled.

For the case of flexible or semi-flexible scheduling, each SI MAC-c PDUmay be associated with a specific transmission time window when the PDUshall be transmitted over the Uu interface. Hence, within the PQassociated with these PDUs, the MAC-c PDUs may have an associatedtransmission time window when PDUs need to be transmitted. The schedulermay then need to ensure that priority is given to the PQ with SI MAC-cPDU to meet the transmission window requirement. One example of such anHS scheduler is to let data in SI MAC-c PQs have rather low priorityuntil the end of the allowed scheduling window is approaching, when thepriority is increased to ensure that the data will be scheduled withinits allowed window.

For any broadcast information, it is important that all UEs in the cellcan be reached. Since the TTI is so short on HS-PDSCH, the bit ratetransmitted in a TTI can be quite substantial, even if small transportblocks are used. This can cause problems with coverage, since in generalthe higher the bitrate, the worse the coverage is.

To increase the coverage, autonomous retransmissions (i.e.,retransmissions not triggered by any NACK feedback) together with softcombining of the transmissions in the UE can be utilized. In itssimplest form, the UE may be informed that a certain amount ofautonomous retransmissions are applied, e.g., data that is addressed toTTI X will be repeated in TTIs X+1, X+2, X+3. Another alternative is tosend repetitions in each 6^(th) TTI if the UE is using 6 HARQ processes.If the UE knows in advance what autonomous retransmissions that areapplied, then soft combining can be applied even if no HS-SCCH istransmitted. If HS-SCCH is transmitted, the UE may know from the newdata indicator of the HS-SCCH information if the transmission is a newtransmission or is to be soft combined with some earliertransmission(s). The retransmissions can be done either using chasecombining or incremental redundancy. However, to really benefit incoverage, the UE may soft combine as many transmissions as possible toarrive at decoding where the CRC check is successful.

To reduce the HS-SCCH overhead when using autonomous retransmissions, itis possible to include a HIS-SCCH only with the first transmission andthen use the same TFRC for the first transmission as well as allretransmissions. If the UE has knowledge in advance of when theretransmissions will occur, it can then use the knowledge that the TFRCsignaled in the single HS-SCCH detected applies for multiple known TTIs,which the UE then can soft combine.

On-Demand SI Distribution

The system information can be divided into static parts that remainunchanged over long times, and dynamic parts that are updated quitefrequently. See fourth SIB embodiment above. In practice, the UE willneed to read static SI quite seldom, typically when entering cells theUE has not been in recently (UEs typically remember the SI from cells ithas recently visited, to avoid having to read the SI again whenreturning to the cell). In order to save downlink capacity, one idea isto not continuously distribute the static SI, but instead onlydistribute it when a UE requests it (referred to as on-demand SIdistribution). This can avoid the continuous transmission of informationthat no UE is listening to, which is a waste of resources.

When the UE needs to read SI that is distributed on demand, the UE maysend an SI distribution request on the uplink. In one preferredembodiment, this message may be transmitted on the Random Access Channel(RACH) channel, in another preferred embodiment this message istransmitted on the E-DCH channel. Preferably, the SI distributionrequest is terminated by the RBS, since the RBS is in charge of systeminformation distribution, and a fast response to the request ispreferred. This implies that preferably the SI distribution request willnot be forwarded to the RNC, as would normal RACH/E-DCH data. However,forwarding the request to the RNC and make the RNC responsible for theresponse is still possible, albeit less preferred alternative.

The SI distribution request can be a specific preamble, using a specificsignature and/or access slot. In that case, the existence of such apreamble is an indication that this is a SI distribution request. Anoptional RACH/E-DCH message can follow as described in the following.

Another possibility is to let the SI distribution request be part of theRACH/E-DCH message payload.

When RACH is used, the MAC PDU transferred in the RACH transport blockhas the form outlined in FIG. 7 and FIG. 8. In one preferred embodiment,the two first bits in the detected RACH message transport block may beused to convey a SI distribution request. These two bits contain theTCTF field of the MAC header, and in current specifications only values00 and 01 are used. A value 10 or 11 could be used to indicate that themessage is a SI distribution request message. This would enable the RBSto quickly detect a SI distribution request without having to unwrapseveral protocol layers to find a signaling message on RRC-level.

When E-DCH is used, the MAC-i PDUs transferred in the E-DCH transportblock has the form outlined in FIGS. 9-11. In particular, in the MAC-iheader 0, the first four bits may be set to a predetermined value, e.g.,1111. Following these bits is a spare field of four bits (which shouldbe set to a predetermined value, e.g., 0000, in current 3GPP releases),and then follows an E-RNTI field.

In one embodiment, a MAC-i header 0 may be used with a value other than0000 in the spare field to indicate a SI distribution request. Inanother embodiment, a value different than 0000 in the spare bits may beused to indicate that the subsequent bits do not include an E-RNTI, butrather includes an SI distribution request. This would enable the RBS toquickly detect a SI distribution request by just identifying bits1111xxxx (where xxxx is different from 0000) in the beginning of thetransport block, hence eliminating the need to unwrap several protocollayers to find a signaling message on RRC-level.

In its simplest form, the SI distribution request message may beimplemented as a simple flag indicating that all on-demand SIs arerequested.

In more advanced forms, the request can be more specific, requesting aset of SIs, where these SIs can correspond e.g., to a subset of SIBs(“SIB33 and SIB42 but no other SIBs”) or different specific parts of theSIB-S. In the more advanced form, several bits of information may needto be transmitted on uplink. In one exemplary embodiment these bitsindicating which set of SIs that are requested may follow directly afterthe TCTF field in the MAC header on RACH. In other exemplaryembodiments, these bits indicating which set of SBs that are requestedmay follow in the four spare bits directly after the 4-bit LCH-ID0 fieldin the MAC-i header 0 on E-DCH, or in the bits directly after the 4-bitLCH-ID0 field and 4-bit spare field in the MAC-i header 0 on E-DCH.

In another embodiment, when a specific signature/access slot is used forSI distribution request, the actual RACH/E-DCH message part can includethe required bits that indicate which set of SIs that are requested. Inthis case, the RBS may decode the transport block, check the CRC and ifCRC is ok then assume this is a valid SI distribution request and theninterpret the different bits in the decoded message as flags for whichset of SIs that have been requested.

A special case may be to just let CRC-OK lead the RBS to retransmit allon-demand SI. This can be useful if detection of a specificsignature/access slot is prone to false alarm, and a sanity check isperformed on the message part. If the correct preamble is detected, theRBS may proceed to decode the RACH/E-DCH message part transport blockaccording to the predefined format. For example, the message can be justa CRC appended to zero information bits. In the case a specific preambleis used for SI distribution requests, the role of the specific preamblemay be to trigger the RBS to attempt to detect a message part that maydiffer in format from the normal RACH/E-DCH. The SI distribution requestmay be decoded and understood by the RBS, while in the case of a normalRACH/E-DCH transmission, the transport block contents may be forwardedto RNC for further unwrapping of protocol layers.

One potential issue with UEs sending SI distribution requests is thatmany UEs can request that same SI information at the same time, causinga high uplink load. As an illustration, consider a case of a train withmany UEs arriving into a new cell. All UEs on that train would like toread SI for the new cell.

In order to avoid this unnecessary uplink load, the RBS can, accordingto one embodiment, be given the possibility to block UEs from sending SIdistribution requests. This can be accomplished by introducing an RBScontrolled flag in the downlink denoted as SI distribution in progressflag. In this embodiment, the UE may be required to read the SIdistribution in progress flag before attempting to send the SIdistribution request. If the flag indicates that SI distribution is inprogress, the UE may be required to refrain from sending the SIdistribution request.

In the train scenario, the first UE to send a SI distribution requestmay trigger the RBS to block further SI distribution requests using theSI distribution in progress flag. There may be a short time between thefirst UE's request before the flag is updated on the downlink and readby all other UEs. Hence, during a short transition time there may beseveral SI distribution requests, but many UEs will be blocked fromloading the uplink with useless requests (the RBS will anyway start todistribute the requested SI) (see FIG. 12).

Hence, in this embodiment, as soon as a UE is missing SIB informationbecause it has never been read or the value tag has changed, the UE maybe required to first monitor the SI distribution in progress flag, andif SI distribution is not already in progress (or soon to start), the UEthen may send its SI distribution request.

FIG. 12 indicates one repetition of the SI after reception of the SIdistribution request, and that the SI distribution in progress flag iscleared after all repetitions of requested SIs are finished. It is alsopossible to envision that the flag should be cleared as soon as the lasttransmission of a particular SI part is finished, to enable UEs thatmissed the earlier parts (that will not be repeated) to request them assoon as possible.

There are multiple possibilities for how to send the SI distribution inprogress flag over the Uu interface. In a preferred embodiment, thecurrently unused bits on an already existing channel such as the PagingIndicator Channel (PICH) or Acquisition Indicator Channel (AICH). A PICHradio frame is 10 ms long and contains 300 bits. However, only the first288 are used for paging information. The SI distribution in progressflag can be mapped on the remaining 12 bits (or some parts thereof), forexample with simple repetition coding of one bit of information (seeFIG. 13).

An AICH access slot is 20/15 ms long, where only the first 4096 chipsare used to transmit A1 s. The remaining 1024 chips (or some partsthereof) of the access slot could house the SI distribution in progressflag (see FIG. 14).

Yet another embodiment would be to use the DTX-parts of the P-CCPCH tocarry the flag. A P-CCPCH slot is 2560 chips long, but out of these, thefirst 256 chips are currently not transmitted, and can house 2 bits ofinformation. The SI distribution in progress flag can be mapped to thesebits in one or several slots (see FIG. 15).

If the SI distribution request message is in the form of a single flagindicating that all on-demand SIs are requested, the SI distribution inprogress flag needs to only be one bit. In more advanced forms, when therequest can be more specific, requesting a set of SIs, a more advancedSI distribution in progress flag may be required. In this case, multiplebits indicating which set of SIs that are being distributed may benecessary. Hence, in these cases, multiple bits may be put on thedownlink physical channel used for the flag(s). It is possible to firstmap the combination of flags per set of SIs to different code words, andthen map these code words on the physical channel bits.

Another possibility (and embodiment) is to let a multi-bit SIdistribution in progress flag provide information of the number ofremaining repetitions of the ongoing SI distribution. In its mostelaborate form, this advanced flag may indicate exactly the remainingnumber of repetitions. A simpler version could be that the advanced flagindicates whether multiple or a single repetition remain (e.g., one outof ‘multiple repetitions left’ and ‘only the last repetition left’). Yetanother option could be that the multi-bit flag also could indicate zerorepetitions left, in case the last repetition has already started.

In certain scenarios (e.g., cells with high amount of mobility), it maybe beneficial to refrain from using the on-demand SI distribution. Onealternative is to indicate on the first distribution channel (e.g., inthe MIB) whether or not the on-demand SI distribution may be used on thesecond distribution channel. If on-demand SI distribution is notconfigured, then no power in downlink will have to be allocated to carrythe SI distribution in progress flag, and there will be no additionaluplink load from SI distribution requests.

If the second distribution channel is configured to use on-demand SIdistribution, it is possible to avoid the uplink load from requests bycontinuously distributing the SI information and continuously sending aSI distribution in progress flag that indicates that SI distribution isin progress. This in effect disables the on-demand ST distributionmechanism.

When second distribution channel is configured to use on-demand SIdistribution, it is even possible to adapt the distribution dynamicallyto the current situation in the cell. The behavior can e.g., beconnected to the cell load in uplink and downlink. If uplink iscurrently the limiting link, the RBS can disable on-demand SIdistribution according to the method in the previous paragraphs. Ifdownlink is the limiting link, it may be more important to not sufferfrom any unnecessary SI distribution, and then the RBS may employon-demand SI distribution in the normal way (as shown in FIG. 12 above).

FIG. 16 illustrates an example method 100 implemented by a network nodein a wireless communication network of transmitting system informationto a plurality of wireless terminals. According to the method 100, thenetwork node transmits a first group of SIBs via a first physicalchannel (block 102), and transmits a second group of additional SIBs viaa different, second physical channel (block 104).

In one or more embodiments, the first physical channel is configured tobe read by a first group of wireless terminals and also by a different,second group of wireless terminals (e.g., the “legacy distributionchannel” discussed above), and the second physical channel is configuredto be read by only one of the first and second group of wirelessterminals (e.g., the “extended distribution channel” discussed above).In one example, the first physical channel is the P-CCPCH, and thesecond physical channel is one of the S-CCPCH and the HS-PDSCH.

In one or more embodiments, the method 100 also includes the networknode transmitting, via the first physical channel, schedulinginformation for reception of the additional SIBs on the second physicalchannel (see, e.g., FIG. 2a ). The scheduling information may beincluded in a scheduling block transmitted via the first physicalchannel (e.g., SB-BC1 in FIG. 2a ).

In one or more embodiments, the method 100 also includes the networknode transmitting, via the second physical channel, schedulinginformation for reception of the additional SIBs (e.g., SB-BC2 in FIGS.3a and 4a ), and also transmitting, via the first physical channel,either additional scheduling information for reception of the additionalSIBs (e.g., SB-BC1 in FIG. 3a ) or an indication that the additionalSIBs are going to be transmitted via the second physical channel (asdescribed above in connection with FIG. 4a ).

In one or more of the embodiments discussed above, transmitting thesecond group of additional SIBs via the second physical channel (block104) includes transmitting, via the second physical channel, one or morefirst SIBs that only include static system information (e.g., SIB-S inFIG. 5a ), and transmitting, via the second physical channel, one ormore second SIBs that only include dynamic system information (e.g.,SIB-D in FIG. 5a ).

In one example, the one or more first SIBs that only include staticsystem information are transmitted according to a first repetitionperiod, and the one or more second SIBs that only include dynamic systeminformation are transmitted according to a different, second repetitionperiod.

In the same or another example, the one or more first SIBs comprise asingle first SIB that includes all static system information (e.g.,SIB-S in FIG. 5a ), and the one or more second SIBs comprise a singlesecond SIB that includes all dynamic system information (e.g., SIB-D inFIG. 5a ).

In one or more embodiments, the method 100 also includes performing loadbalancing between the first and second physical channels by including aSIB from the first group of SIBs in the second group of additional SIBs.

FIG. 17 illustrates an example method 200 implemented by a wirelessterminal in a wireless communication network of processing systeminformation. According to the method 200, the wireless terminalprocesses information received from a base station over a first physicalchannel to identify a first group of system information blocks (SIBs)(block 202), and also processes information received from the basestation over a different, second physical channel to identify a secondgroup of additional SIBs (block 204).

In one or more embodiments, the first physical channel is configured tobe read by a first group of wireless terminals and also by a different,second group of wireless terminals (e.g., the “legacy distributionchannel” discussed above), and the second physical channel is configuredto be read by only the second group of wireless terminals (e.g., the“extended distribution channel” discussed above). In such embodiments,the wireless terminal is part of the second group of wireless terminals.In one example, the first physical channel is the P-CCPCH, and thesecond physical channel is one of the S-CCPCH and the HS-PDSCH.

In one or more embodiments, the wireless terminal identifies the secondgroup of additional SIBs based on processing information received fromthe base station over the first physical channel to identify schedulinginformation for reception of the additional SIBs on the second physicalchannel (see, e.g., FIGS. 2a and 3a ).

In one or more embodiments, the method 200 also includes the wirelessterminal processing information received from the base station over thesecond physical channel to identify scheduling information for receptionof the additional SIBs (e.g., SB-BC2 in FIGS. 3a and 4a ). In theseembodiments, the method also includes processing information receivedfrom the base station over the first physical channel to identify eitheradditional scheduling information for reception of the additional SIBs(e.g., SB-BC1 in FIG. 3a ) or an indication that the additional SIBs aregoing to be transmitted via the second physical channel (as describedabove in connection with FIG. 4a ).

In one or more embodiments, the processing of information received fromthe base station over the second physical channel to identify the secondgroup of additional SIBs (block 204) includes identifying, from theinformation received over the second physical channel, one or more firstSIBs that only include static system information (e.g., SIB-S in FIG. 5a), and identifying, from the information received over the secondphysical channel, one or more second SIBs that only include dynamicsystem information (e.g., SIB-D in FIG. 5a ).

In one example, the one or more first SIBs that only include staticsystem information are received according to a first repetition period,wherein the one or more second SIBs that only include dynamic systeminformation are received according to a different, second repetitionperiod.

In the same or another example, the one or more first SIBs comprises asingle first SIB that includes all static system information (e.g.,SIB-S in FIG. 5a ), and the one or more second SIBs comprises a singlesecond SIB that includes all dynamic system information (e.g., SIB-D inFIG. 5a ).

Nodes and Terminals

The methods illustrated above may be performed by one or more networknodes and/or wireless terminals. The network node can be a RNC or RBS.Of course, these are merely examples of network nodes and should be nottaken in a limiting sense.

FIG. 18a illustrates an embodiment of a network node capable ofdistributing system information utilizing legacy and extendeddistribution channels according to one or more of the techniquesdescribed above. The example network node may include a controller, acommunicator and a SI (system information) manager. The communicator maybe structured to perform radio communications with wireless terminalsvia one or more antennas. The communicator may also be structured toperform wired and/or wireless communication with other network nodes.The SI manager may be structured to manage system information and totransmit, via the communicator, system related information (e.g., MIB,SB-BC1, SB-BC2, SIBs, SIB-S, SIB-D, etc.) to one or more wirelessterminals. The SI manager may also respond to SI related requests fromthe wireless terminals. The controller may be structured to control theoverall operation of the network node.

FIG. 18a provides a logical view of the network node and the componentsincluded therein. It is not strictly necessary that each component beimplemented as physically separate modules. Some or all components maybe combined in a physical module.

Also, the components of the network node need not be implementedstrictly in hardware. It is envisioned that the components can beimplemented through any combination of hardware and software. Forexample, as illustrated in FIG. 18b , the network node may include oneor more hardware processors, one or more storages (internal, external,both), and one or both of a wireless interface (in case of a radio node)and a network interface.

The processor(s) may be configured to execute program instructions toperform the functions of one or more of the network node components. Theinstructions may be stored in a non-transitory storage medium or infirmware (e.g., ROM, RAM, Flash) (denoted as storage(s)). Note that theprogram instructions may also be received through wired and/or orwireless transitory medium via one or both of the wireless and networkinterfaces. The wireless interface (e.g., a transceiver) may beconfigured to receive signals from and send signals to wirelessterminals via one or more antennas. The network interface may beincluded and configured to communicate with other network nodes.

FIG. 19a illustrates an example embodiment of a wireless terminalcapable of processing system information according to one or more of thetechniques described above. The wireless terminal of FIG. 19a includes acontroller, a communicator and a SI manager. The communicator may bestructured to perform radio communications with other radio nodes suchas RBS. The SI manager may be structured to receive, via thecommunicator, SI related information. The SI manager may also requestthe network node for SI related information. The controller may bestructured to control the overall operation of the network node.

As illustrated in FIG. 19b , the wireless terminal may include one ormore hardware processors, one or more storages, and a wirelessinterface. The processor(s) may be configured to execute programinstructions to perform the functions of one or more of the network nodecomponents. The instructions may be stored in a non-transitory storagemedium or in firmware (e.g., ROM, RAM, Flash) (denoted as storage(s)).Note that the program instructions may also be received through wiredand/or or wireless transitory medium via one or both of the wireless andnetwork interfaces. The wireless interface (e.g., a transceiver) may beconfigured to receive signals from and send signals to wirelessterminals via one or more antennas.

One significant advantage (among others) of using the extended systeminformation distribution mechanism is that the system informationcapacity is increased while maintaining backwards compatibility forexisting UEs.

As discussed above, in one or more aspects, a plurality of channels maybe used to distribute system information. One or more of thesedistribution channels may be used to maintain backwards compatibility.Also, one or more distribution channels may be used to extend the systeminformation distribution.

Some or all aspects of the disclosed subject matter may be applicable ina wireless network comprising one or more network nodes (e.g., RNC,RBS). An aspect of the disclosed subject matter may be directed to oneor more methods performed by a network node. For example, the networkmay:

-   -   transmit MIB/SB (which may include information of SIBs) over a        legacy distribution channel, and transmit corresponding SIBs        over an extended distribution channel;    -   transmit MIB/SB (which may include information of SBs) over a        legacy distribution channel, transmit corresponding SBs (which        may include information of SIBs) over an extended distribution        channel, and transmit corresponding SIBs over the extended        distribution channel;    -   transmit MIB/SB (which may include an indication that extended        ST information is available) over a legacy distribution channel,        transmit SB (which may include information of SIBs) over an        extended distribution channel, and transmit corresponding SIBs        over the extended distribution channel;    -   transmit MIB/SB (which may include an indication that extended        SI information is available) over a legacy distribution channel,        transmit SIB-S (which may include static information) over an        extended distribution channel, and transmit SIB-D (which may        include dynamic information) over the extended distribution        channel.

Another aspect of the disclosed subject matter may be directed toprogram instructions which when executed by a computer of a networknode, causes the network node to perform the method as described above.The program instructions may be received through a transitory medium andexecuted directly therefrom. The program instructions may also be storedin a non-transitory storage medium and the network node may read theprogram instructions therefrom.

Another aspect of the disclosed subject matter may be directed to one ormore methods performed by a wireless terminal in a wireless network toreceive SIBs. For example, the wireless terminal may:

-   -   read/decode MIB/SB (which may include information of SIBs)        received over a legacy distribution channel, and read/decode        corresponding SIBs received over an extended distribution        channel;    -   read/decode MIB/SB (which may include information of SBs)        received over a legacy distribution channel, read/decode        corresponding SBs (which may include information of SIBs)        received over an extended distribution channel, and read/decode        corresponding SIBs received over the extended distribution        channel;    -   read/decode MIB/SB (which may include an indication that        extended SI information is available) received over a legacy        distribution channel, read/decode SB (which may include        information of SIBs) received over an extended distribution        channel, and read/decode corresponding SIBs received over the        extended distribution channel;    -   read/decode MIB/SB (which may include an indication that        extended SI information is available) received over a legacy        distribution channel, read/decode SIB-S (which may include        static information) received over an extended distribution        channel, and read/decode SIB-D (which may include dynamic        information) received over the extended distribution channel.

Another aspect of the disclosed subject matter may be directed toprogram instructions which when executed by a computer of a wirelessterminal, causes the wireless terminal to perform the method asdescribed above. The program instructions may be received through atransitory medium and executed directly therefrom. The programinstructions may also be stored in a non-transitory storage medium andthe network node may read the program instructions therefrom.

The present disclosure may, of course, be carried out in other ways thanthose specifically set forth herein without departing from essentialcharacteristics of the disclosure. The present embodiments are to beconsidered in all respects as illustrative and not restrictive, and allchanges coming within the meaning and equivalency range of the appendedclaims are intended to be embraced therein.

What is claimed is:
 1. A method implemented by a User Equipment in awireless communication network, the method comprising the steps of:receiving, from a base station and over a first physical channel, systeminformation in a Master Information Block (MIB) said MIB comprisingscheduling information for reception of a system information block (SIB)on a different, second physical channel; obtaining schedulinginformation in the SIB received on the second physical channel,indicating that additional system information blocks (SIBs) aredistributed on demand on the second physical channel; sending a systeminformation (SI) distribution request to the base station; receiving theadditional system information blocks (SIBs) on said second physicalchannel.
 2. The method of claim 1, wherein the system informationdistribution request is sent on a Physical Random Access Channel(PRACH).
 3. The method of claim 2, wherein the SI distribution requestis a specific random access (RA) preamble and/or access slot.
 4. Themethod of claim 1, wherein the SI distribution request is implemented torequest a subset of SI messages.
 5. A method implemented by a basestation in a wireless communication network, the method comprising thesteps of: transmitting, to a User Equipment and over a first physicalchannel, system information in a Master Information Block (MIB) said MIBcomprising scheduling information for reception of a system informationblock (SIB) on a different, second physical channel; wherein the SIB onthe second physical channel includes scheduling information indicatingthat additional system information blocks (SIBs) are distributed ondemand on the second physical channel; receiving a system information(SI) distribution request from the User Equipment; transmitting theadditional system information blocks (SIBs) on the second physicalchannel.
 6. The method of claim 5, wherein the system informationdistribution request is sent on a Physical Random Access Channel(PRACH).
 7. The method of claim 6, wherein the SI distribution requestis a specific Random Access (RA) preamble and/or access slot.
 8. Themethod of claim 5, wherein the SI distribution request is implemented torequest a subset of SI messages.
 9. A User Equipment, comprising: atransceiver configured to receive, from a base station and over a firstphysical channel, system information in a Master Information Block (MIB)said MIB comprising scheduling information for reception of a systeminformation block (SIB) on a different, second physical channel;processing circuitry coupled to the transceiver and operable to obtainscheduling information in the SIB received on the second physicalchannel, indicating that additional system information blocks (SIBs) aredistributed on demand on the second physical channel; and thetransceiver further configured to: send a system information (SI)distribution request to the base station; and receive the additionalsystem information blocks (SIBs) on said second physical channel. 10.The User Equipment claim 9, wherein the system information distributionrequest is sent on a Physical Random Access Channel (PRACH).
 11. TheUser Equipment of claim 10, wherein the SI distribution request is aspecific Random Access (RA) preamble and/or access slot.
 12. The UserEquipment of claim 9, wherein the SI distribution request is implementedto request a subset of SI messages.
 13. A base station, comprising: atransceiver coupled to processing circuitry, the transceiver configuredto: transmit, to a User Equipment and over a first physical channel,system information in a Master Information Block (MIB) said MIBcomprising scheduling information for reception of a system informationblock (SIB) on a different, second physical channel; wherein the SIB onthe second physical channel includes scheduling information indicatingthat additional system information blocks (SIBs) are distributed ondemand on the second physical channel; receive a system information (SI)distribution request from the User Equipment; and transmit theadditional system information blocks (SIBs) on the second physicalchannel.
 14. The base station of claim 13, wherein the systeminformation distribution request is sent on a Physical Random AccessChannel (PRACH).
 15. The base station of claim 14, wherein the SIdistribution request is a specific Random Access (RA) preamble and/oraccess slot.
 16. The base station of claim 13, wherein the SIdistribution request is implemented to request a subset of SI messages.